Water-Based Lubricants for Conveyor Belts

ABSTRACT

The invention relates to water-based lubricants for conveyor belts. More particularly, the invention relates to water-based lubricants for conveyor belts for the drinks industry.

The invention relates to water-based lubricants for conveyor belts. More particularly, the invention relates to water-based lubricants for conveyor belts for the drinks industry.

Lubricants for conveyor belts for the drinks industry have to meet high demands, especially with regard to their fitness for contact with and compatibility with food and drink. For lubrication of conveyor belts in dispensing lines in the drinks industry, according to the application methodology, either lubricant oils or emulsions/dispersions diluted with water to different degrees are used. WO 2007/040678 A1 describes such a concept. This comprises silicone emulsions that are diluted with water. According to the degree of dilution, this is then referred to as wet or semidry lubrication. In the case of wet lubrication with typical dilutions of the lubricant of 1:100 to 1:1000, water consumption is very high. The case of dilution of less than 1:100 is referred to as semidry lubrication. In both cases, it should be noted that the hardness of the water added has a crucial effect on the performance and compatibility of the lubricant with the packaging material transported. Accordingly, in the case of a wet or semidry lubricant, it is typically necessary to add elevated amounts of free organic acids in order to neutralize the water hardness-related alkalinity. However, disadvantages of emulsions or suspensions are that stirrer units are frequently required in the blending with water, and that they have poorer storage stability than homogeneous solutions. Moreover, it is not possible to achieve a continuous film of the lubrication-active component on the conveyor chain, which has an adverse effect on the tribological properties. A common factor to all lubricants mentioned is the relatively complex cleaning of the conveyor belts.

One aim of the present invention was therefore to provide a highly tribologically effective lubricant formulation which is effective in very small amounts and need not be diluted further with water. Thus, a maximum saving of water is possible. Furthermore, the formulation of the invention is biodegradable and usable in the food and drink sector. The formulation is additionally storage-stable, fully soluble in water and easy to remove from the conveyor belts.

These aims are achieved by the provision of a water-based lubricant composition comprising a water content of 50% to 96% by weight, 4% to 40% by weight of at least one viscosifying component and 0.05% to 10% by weight of preservative substances that provide protection from soiling. No solids and no water-insoluble components are present.

The water-based lubricant composition of the invention has good biodegradability and environmental compatibility in an aqueous environment. Moreover, it features good compatibility with application-related materials, such as chain materials, application technology and packaging. The low-temperature characteristics of the aqueous lubricant composition of the invention can be considerably improved by addition of antifreezes, for example low molecular weight glycol or glycerol. In addition, it is possible to add additives in order to control the properties of the lubricant composition of the invention. If desired, the aqueous lubricant compositions of the invention can also be formulated in a foam-free manner.

The lubricant composition of the invention comprises 4% to 30% by weight of at least one viscosifying component and 0.05% to 10% by weight of preservative substances that provide protection from soiling; the remainder is water.

The lubricant composition of the invention may also comprise

0.05% to 15% by weight of antifreeze,

0.05% to 15% by weight of anticorrosive,

0.05% to 5% by weight of defoamer,

0.05% to 5% by weight of wetting agent,

0.05% to 5% by weight of biocides,

0.005% to 2% by weight of fragrances.

The viscosifying component of the lubricant composition of the invention is selected from the group consisting of water-soluble carboxylic esters, or a mixture of water-soluble carboxylic esters and low molecular weight polyalkylene glycols. Preference is given to using water-soluble ethoxylated esters of dicarboxylic acids that are sold under the Nycobase 618 name by Nyco S.A. The low molecular weight polyalkylene glycols used are preferably a polyethylene glycol having a mean molar mass of 200-600, which are sold by Clariant Deutschland GmbH under the PG 200-600 name.

In the case of low-temperature applications, the lubricant composition of the invention may comprise an antifreeze which is selected from the group consisting of mono- and/or polyhydric alcohols and/or alcohol derivatives, for example glycerol or propane-1,2-diol.

Anticorrosives used for the lubricant composition of the invention are neutralized and non-neutralized carboxylic acids, neutralized phosphoric acids and/or phosphoric acid derivatives, benzoic acid and/or benzoic acid derivatives, triazoles, alcoholamines, glycolamines.

Antiwear agents present are water-soluble compounds containing sulfur, phosphorus and/or nitrogen, for example salts of sulfonic acid derivatives and thiols.

For prevention of foam formation, it is possible to use additives, for example polydimethylsiloxanes or polymers of acrylate derivatives.

According to the application, the lubricant composition of the invention may comprise emulsifiers and/or wetting agents, for example foaming or non-foaming emulsifiers from the class of ionic surfactants (e.g. sulfonates) and nonionic surfactants (e.g. fatty alcohol ethoxylates), alkylene oxide polymers, phosphate esters and quaternary ammonium compounds, alkoxylated silicones and silicone derivatives, and carboxylic acid derivatives.

In addition, lubricant composition of the invention may comprise biocides, for example isothiazolone derivatives.

According to the application, it is also possible to use fragrances which are selected from the group consisting of alcohols, aldehydes, ketones, esters, alkenes, salts, e.g. copper salts and/or zinc sulfates.

Preferably, the lubricant composition of the invention comprises 5% to 20% by weight of viscosifying compound and 0.05% to 10% by weight of preservative substances that provide protection from soiling, and also 0.05% to 5% by weight of antiwear agents; the remainder is water.

Especially preferably, the lubricant composition of the invention comprises 7.5% to 15% by weight of viscosifying compound and 0.05% to 10% by weight of preservative substances that provide protection from soiling, and also 0.1% to 1.5% by weight of antiwear agents; the remainder is water.

The lubricant composition of the invention ensures that the performance of the lubricant is not significantly impaired even by production-related flashing with water.

The lubricant composition of the invention additionally features excellent sprayability which can also be employed in unpressurized nozzles and minimizes the risk of blockage of nozzles. Moreover, application is possible by all standard methods, for example nozzles operated with or without compressed air, brushes, slide plates.

The lubricant composition of the invention also brings about excellent protection from wear with all standard chain material/packaging combinations, for example pairing of can/plastic chain, Tetrapack/plastic chain, PET (single-use and multi-use)/plastic chain or steel chain, glass bottle/plastic chain or steel chain.

The lubricant composition of the invention has excellent compatibility with standard packaging, chain materials and application techniques. Furthermore, in the case of use of the lubricant composition of the invention, a distinct improvement is achieved in storage and transport stability, with regard to the effect of temperature and vibration.

The lubricant composition of the invention is also excellent with regard to biodegradability.

The lubricant composition of the invention is described in detail hereinafter with reference to examples.

EXAMPLES

The example formulations are produced by blending the majority of the individual constituents by means of a stirrer and heating to 70° C. for 30 min, followed by cooling and stirring-in of the temperature-critical constituents.

Example 1

Viscosifying component: Nycobase 618 9.27% Antiwear: MPS 0.39% deion. water 90.34%

Example 2

Viscosifying component: Nycobase 618 10.0% Antiwear: MPS 0.4% Biocide: Acticide MBS 0.10% Defoamer: ES 561 1.0% Anticorrosive: M 528 L 2.0% deion. water 86.5%

Example 3

Viscosifying component: Nycobase 618 9.27% Preservative components that SurTec 192 0.5% provide protection from wear: SurTec 055 1.0% deion. water 89.23%

Example 4

Viscosifying component: Nycobase 618 10.0% Viscosifying component: PG 200 2.5% Antiwear: Lubio EP 1 0.5% Biocide: Acticide MBS 0.15% Wetting agent: Hydrolite 5 0.9% Defoamer: ES 561 1.0% Anticorrosive: M 528 L 7.0% deion. water 77.95%

Example 5

Viscosifying component: Nycobase 618 10.0% Antifreeze: Glycerin 2.5% Antiwear: Lubio EP 1 0.5% Biocide: Acticide MBS 0.2% Defoamer: ES 561 1.0% deion. water 85.8%

Example 6

Viscosifying component: Nycobase 618 9.27% Antiwear: MPS 0.39% Preservative components that Redokon CDD A-H 0.014% provide protection from wear: Redokon CDD B 0.001% deion. water 90.325%

The components used are, as already mentioned above, PG 200, Nycobase 618. In addition, M 528 L is used, this being a mixture of various neutralized organic and inorganic acids which is sold by Cortec Corporation. Surtec 192 is a mixture of phosphates, silicates and amine-neutralized organic acids which can be purchased from SurTec Deutschland GmbH. SurTec 055 is a mixture of amines, silicates and hydrocarbons, and also anionic and nonionic surfactants, likewise from SurTec Deutschland GmbH. Hydrolite 5 is a pentanediol from Symrise AG. MPS is a salt of organic sulfur compounds which is sold by Raschig GmbH. Acticide MBS is a mixture of benzisothiazoles and methylisothiazolone from Thor GmbH. Lubio EP1 is a salt of an organic sulfur compound from Schafer Additivsysteme GmbH. ES 561 is a silicon-containing defoamer from Additivchemie Luers GmbH. Glycerol is sourced from Brenntag GmbH. Redokon CDD A-H and Redokon CDD B are chlorine dioxide solutions from Redokon GmbH.

The above example formulations were now tested for their efficacy.

1. Antiwear

The SRV (oscillation/friction/wear) test is a commonly used test for quantification of the antiwear effect of lubricants. This is typically conducted using the steel-steel material pair. In the present case, for better applicability to the application, the POM (polyoxymethylene)/steel material pair is chosen. The wear rate was evaluated after a test duration of 6 hours at a load of 95 N/mm².

TABLE 1 Product Wear rate [mm³/h] Interflon Fin Food lube AL 0.67 (oil-based dry lube made from mineral oil with PTFE) P3 Lubodrive RF 1.72 (oil-based dry lube made from hydrocarbon resin) Neomoscan G7 0.69 (water-based wet lube made from amine acetate) Example 1 0.04 Example 2 0.10

Table 1 shows that all three examples according to the present invention have distinctly lower wear rates than customarily used products.

2. Spreading Characteristics

Good spreading characteristics are indispensable in the case of minimal lubrication volumes for maintenance of a constant lubricant film. Spreading characteristics are typically determined by contact angle measurements on the relative surface. The smaller the contact angle, the better the wetting of the surface.

TABLE 2 Contact angle [°] Product on PBT after 15 s Example 4 38 Example 2 51 Lubostar CP 64 (water-based wet lube made from silicones)

Table 2 shows that the examples of the present invention have significantly better spreading characteristics than the frequently used Lubostar CP wet lube. The studies were conducted on PBT, a commonly used chain material.

3. Tests on Conveying Devices with Various Pairs

Lubrication performance of the water-based example formulation was tested using a standard conveying device from Krones, using various relevant material combinations at room temperature and with a typical chain speed of 0.8 m/sec. The coefficients of friction were each determined using a 1 l glass water bottle with its original seal, a 1.5 l PET disposable bottle and a 1.5 k TetraPack. The container that was grinding against the conveyor chain was fixed to a spring balance with a cord.

TABLE 3 Coefficient of friction averaged over 120 sec with various material pairs POM/ Steel/glass POM/PET TetraPack Example 2 0.11 0.09 0.15 Example 4 — 0.07 0.15

Typically, the coefficients of friction of the various material pairs are in the range of 0.05 to 0.20. Table 3 shows the good lubricity of the compositions examined.

With the lubricant composition according to example 3, by way of evidence of the excellent performance with the least possible lubricant consumption, a 1.5 l PET disposable bottle was tested under the above-described conditions over a period of 4 hours. Over this time, a further 0.05 ml of lubricant was applied every 5 minutes. The coefficient of friction was constantly 0.09+/−0.01 and hence within the ideal range for this material pair.

4. Anticorrosive

In the case of use of water-based lubricants rather than an oil-based dry lubricant, adequate corrosion protection of the application technique should be assured, in order to protect components such as metering valves or spray valves. Typical corrosion protection tests are effected by storing relevant components in the lubricant formulation at elevated temperature.

TABLE 4 Stability of non-stainless steel components from application technology with respect to the lubricant Work steel at 70° C. Anticorrosion after immersion additive for 14 days Example 2 2% by weight adequate Example 4 7% by weight good Example 1 0% by weight unsatisfactory Neomoscan G7 No manufacturer data unsatisfactory

It can be seen in table 4 that adequately additized aqueous lubricant formulations can give adequate protection for corrosion-sensitive application technology.

5. Cleaning

Soiling on food and drink containers should absolutely be avoided for hygienic and cosmetic reasons. Typical soiling includes normal dusts, particles of packaging, leaked food or drink product, wear particles from the chain and guide rail, and lubricant residues.

TABLE 5 Additive for Protection from prevention residue buildup on of soiling conveyor chain Example 3 present adequate Example 1 absent unsatisfactory P3 Lubodrive RF no manufacturer data unsatisfactory Neomoscan G7 no manufacturer data unsatisfactory DryExx SF no manufacturer data unsatisfactory (water-based dry lube)

The lubricants specified in table 5 were used to conduct the buildup of soiling both in continuous operation and in laboratory studies with an original PBT chain on the test conveyor. Surprisingly, a significant reduction in residue buildup was achieved in example 3.

7. Defoamer

Excessive evolution of foam in the application of conveyor lubricants should be avoided owing to reduced tribological efficacy. Foam-forming lubricants also have worse applicability, particularly in the case of use of spray nozzles. The use of a defoamer in example formulation 5 visibly showed a significant reduction in the tendency to foaming.

TABLE 7 Defoamer Visible defoamer effect on the conveyor Example 4 present adequate Example 1 absent unsatisfactory

8. Clarity

All formulations from examples 1 to 6 are clear solutions. The homogeneity of the system gives rise to distinct advantages in storage and transport stability, in homogeneous applicability without use of stirring units, and in avoidance of water-insoluble residues on the conveyor chain in the case of emulsions/suspensions.

TABLE 8 Type Appearance Example 1 solution clear Example 2 solution clear Example 3 solution clear Example 4 solution clear Example 5 solution clear Example 6 solution clear Lubostar CP emulsion cloudy Interflon Fin Food Lube AL suspension cloudy P3 Lubodrive RF solution clear Neomoscan G7 solution clear DryExx SF emulsion cloudy

9. Flashing with Water

The cleaning of conveyor chains typically entails a production shutdown, since the friction characteristics are greatly affected by the amount of water applied and typically deteriorate in the case of elevated humidity. It is also not impossible that water bottles being conveyed will burst and that this will lead to locally limited flashing of the lubricant off the conveyor chain.

TABLE 9 ΔCoF PET/PBT after flashing with excess of water (water:lubricant 500:1) Example formulation 2 +35% DryExx SF +70%

It has been found that, surprisingly, the formulation according to example 2, even in the case of flashing with 500 times the amount of water compared to the amount of lubricant applied to the chain, leads only to moderate deterioration in the coefficient of friction of 35%. This enables uninterrupted filling operation in the case of faults or in the event of cleaning, which was not the case compared to a known lubricant composition, since the coefficient of friction here was worsened by 75%.

10. Applicability

The lubricant composition according to example 5 was applicable either by means of dosage via a metering valve or magnetic valve and subsequent application by means of a guide plate, or else via nozzles operated with compressed air or without compressed air. Particularly the possibility that the composition according to example 4 can be applied by means of compressed air-free nozzles in minimal amounts distinguishes this formulation from frequently used standard products, for example DryExx SF or P3 Lubodrive RF.

11. Compatibility with Packaging, Application Technology and Chain Material

For further testing of the properties of the lubricant compositions of the present invention, immersion tests were conducted with gasket material, hose material, pipe elements, nozzle constituents, pump membranes and magnetic valves from standard application technology and POM chain material at 70° C. over 4 weeks with example formulation 5. No changes in the materials were detected.

For container compatibility, 1.5 l PET disposable bottles with the original seal, 1 l glass bottles, 0.5 l can and 0.5 lTetraPack were placed onto a glass surface wetted with formulation according to example 5 for 30 sec and then stored on a clean glass surface for 72 hours. Then there was a visual examination for changes to the material, such as stress, cracking or discoloration. In no case were any noticeable features observed.

12. Biodegradability

All the example formulations mentioned are environmentally compatible and biodegradable to a high degree by virtue of the high water content, and by virtue of the very good biodegradability of the viscosifying agents used. 

1. Water-based lubricant composition for conveyor belts, comprising: 4% to 30% by weight of at least one viscosifying component, 0.05% to 10% by weight of preservative substances that provide protection from soiling, water to 100% by weight, characterized in that the viscosifying component is a water-soluble carboxylic ester, or a mixture of a water-soluble carboxylic ester and a low molecular weight polyalkylene glycol.
 2. Lubricant composition according to claim 1, further comprising one or more components selected from the group consisting of: 0.05% to 5% by weight of antiwear agent, 0.05% to 15% by weight of antifreeze, 0.05% to 15% by weight of anticorrosive, 0.05% to 5% by weight of antiwear agent, 0.05% to 5% by weight of defoamer, 0.05% to 5% by weight of wetting agent, 0.05% to 5% by weight of biocides, 0.005% to 2% by weight of fragrances.
 3. Lubricant composition according to claim 1, characterized in that the preservative substances that provide protection from soiling are a compound or mixture selected from the group consisting of foaming or non-foaming emulsifiers from the class of ionic and nonionic surfactants.
 4. Lubricant composition according to claim 2, characterized in that the antiwear agent is a water-soluble compound containing sulfur, phosphorus and/or nitrogen.
 5. Lubricant composition according to claim 2, characterized in that the antifreeze is a compound selected from the group consisting of mono- and polyhydric alcohols and derivatives thereof.
 6. Lubricant composition according to claim 2, characterized in that the anticorrosive is a compound selected from the group consisting of neutralized and non-neutralized carboxylic acids, neutralized phosphoric acids and/or phosphoric acid derivatives, benzoic acid and/or benzoic acid derivatives, triazole, alcoholamines, glycolamines.
 7. Lubricant composition according to claim 2, characterized in that the defoamer is a compound selected from the group consisting of polysiloxanes or polymers of acrylate derivatives, the wetting agent used is a compound selected from the group consisting of ionic and nonionic surfactants, the biocide used is isothiazolone derivatives, and the fragrance used is a compound selected from the group consisting of alcohols, aldehydes, ketones, esters, alkenes, copper salts and/or zinc salts.
 8. Use of the lubricant composition according to claim 1 in undiluted form.
 9. Use of the lubricant composition according to claim 1 in a dilution of 1:1000.
 10. Use of the lubricant composition according to claim 2 in undiluted form.
 11. Use of the lubricant composition according to claim 2 in a dilution of 1:1000. 